Add imx_ocotp_sense_enable() function to allow changing that aspect of
OCOTP driver behaviour before calling imx_ocotp_read_field()

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Add functions to access the OCOTP fuses field wise, similar to what has
been done for the IIM. Also add a i.MX6 fusemap header file.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>